Radio receiving system



Feb. 18, 1947. L. COHEN l RADIO RECEIVING SYSTEM Filed Oct. 22, 1943 aalo Fece/Ver.

Pda/fo Fece/Ver.

Patented Feb. 18, 1947 RADEO RECEIVING SYSTEM Louis Cohen, Bethesda, Md. l

Application October 22, 1943, Serial No. 507,289

(Cl. Z50-20) 13 Claims. l

This invention relates to the art of radio signaling.

It has for its object providing improved methods and means for the reception of radio signals.

A further object is the elimination of foreign electrical interferences in the reception of radio signals,

Still another object -is the elimination of interferences caused by static disturbances, such as atmospheric discharges.

The accompanying figures show typical diagrammatical circuit systems whereby the novel method employed in the invention is made effective in realizing the `objective of the elimination of interferences in radio reception.

Fig, 1 is an embodiment of the invention showing a combination of a wave conductor antenna and a simple antenna associated with a receiving circuit system.

Fig. 2 is a modification providing for a ground connection of the wave conductor.

Fig. 3 is still another modication in which the wave conductor is coupled to the input circuit of the receiver.

Fig. 4 is a sectional View of an adjustable wave conductor which may be used in the circuit arrangements shown in Figs. 1 to 3;

In all the figures, the same numbers designate similar elements.

In Fig. l, l designates a simple antenna, suitable for broadcast range of frequencies 500 kc. to 1500 kc. A short wire of to 20 kis quite adequate. 2 is a wave coil or wave conductor, that is, a coil of sufficient length of wire in relation to the wave lengths of the signals to be received, to effect a wave development on it by the high frequency signals. Associated with the wave conductor 2 is a, metal plate lil, the proximity of which to the Winding of the wave coil may be varied, thereby effecting a variation in the distributed capacity of wave conductor 2 and so effecting a variation in the electrical length of wave conductor 2. To simplify the drawing one means for varying the proximity between metal plate lil and Wave conductor 2 is shown; any mechanical arrangement for varying the distance separation between 2 and lll will serve the purpose. -l l is another simple antenna which is connected to metal plate lll and through the electrostatic coupling transmits the radiant energy collected on antenna ll to wave conductor 2. The combination of wave conductor 2 and antenna l l, each of which picks up radiant energy, can be considered as an artificial antenna system. The wave conductor 2 is connected to antenna l at the junction point 3, to which point is connected an oscillating circuit of inductance i and capacity 5 in parallel, functioning as the input circuit of a radio receiver d which may be of any desired type known in the art, such as radio frequency ampliier receivers, superheterodyne receivers, etc. The terminals 5, l of the oscillating circuit Ll, 5 are connected to grid and filament of the rst amplifier tube of the receiving set il.

By a suitable adjustment of the oscillating circuit fi, 5 and the proximity between metal plate lll and wave conductor 2, a condition is obtained whereby the system is tuned to the particular signals which are desired to be received, at the same time effectively screening out interference effects, such as atmospheric discharges and others which would normally find their way into the receiver and interfere with the reception of the desired signals. The method is adapted for use in the reception of telegraphic signals as well as telephonie signals, such as broadcast reception.

A complete explanation of the phenomena involved in the operation of the circuit system described above would require a mathematical discussion of considerable complexity. The study of the pro-pogation of electric impulses on a conductor of distributed inductance and capacity in its simplest form presents formidable difficulties and particularly so when dealing with a complicated circuit network such as disclosed herein.

Without, however, attempting to present a mathematical analysis of the phenomena involved, it can be stated in a rgeneral way that a mathematical study leads to the conclusion that for relatively low frequency impulses such as atmospheric discharges, the voltages developed on antenna l and wave conductor oppose their effects at the junction point 3 and hence do not produce any effect on the oscillation circuit Il, 5 which is associated with an amplifier and detector. For radio signals which are of relatively high frequency, the wave developments set up on wave conductor 2 and antenna l are in such phase relation at the junction point 3 to be additive in their effects on the oscillating circuit il, 5, or at least the high frequency energy at point 3 collected by the plurality of antennae d0 not balance out; Further, because lthe low frequency discharges do not aiect the circuit ll, the frequency of the oscillations generated by suchlow frequency discharges is controlled solely by wave conductor i3 vand antenna l, which is of different order from the natural frequency of the system which is governed by the entire electric circuit system including the oscillating circuit 4, 5. Thus, oscillations generated by electric discharges are of a frequency different from the resonant frequency of the circuit system and accordingly do not affect the receiving system. We have therefore a condition whereby neither the interfering impulses in their initial action, nor the oscillations subsequently generated by these impulses, have any effect on the input of the radio receiver. Irrespective, however, of the theoretical explanation of the functioning of the circuit system disclosed herein, I have demonstrated experimentally in many tests, that using this circuit system and suitably adjusting the various elements, a condition is obtained whereby good radio reception, free from interference, can be had under diflicult static conditions.

Fig. 2 is a modification in which the antenna Il is grounded at I3. In this arrangement the antenna ll serves as a ground connection for the metal plate lil which aiects the tuning of the wave conductor 2 and also serves as a radiant energy collector for any energy transmitted through ground or air. Sufficient signal energy, is picked up by the grounded connection to give good signal reception. At the same time, static discharges and other interferences are also picked up in the same manner, and these are balanced out by the interfering impulses which act simultaneously on antenna I. I find this circuit arrangement highly eiective in the elimination of interferences and at the same time emcient for signal reception; the operation and adjustments are the same as in Fig. 1. Y

Fig. 3 shows an additional modification in which provision is 'made for coupling of wave conductor 2 to the oscillating circuit 4, 5. A metal strip lli movable along wave conductor 2 is connected through wire l to the coupling coil it. In this way the oscillating circuit 5 is put in inductive relation to the wave conductor 2. The energy of the wave conductor is transmitted through the condenser coupling of strip hi and the inductive coupling of coils I6 and 4 to the oscillating circuit 4, 5. The condenser coupling between metal strip I4 and wave coil 2 is adjustable by providing means for sliding the metal strip I4 along wave conductor 2 and also adjusting the spacing between 2 and lil. Further the inductive relation between l5 and ll may be also varied in any suitable manner. By the suitable adjustment of I4 in relation to 2 and the mutual inductance between I6 and 4, a further improvement is obtained in the elimination of interferences.

Fig. i is a sectional drawing of a typical embodiment of an adjustable wave conductor. The wave coil 2 is mounted between insulated plates 22, 23 which are supported on the insulated base 2l. The metal plate IG is hinged `at 2l to plate 22; the opposite end thereof, which is of smaller width than the main body of the plate, extends through slot 28 at the lower portion of plate 23 to permit the movement of plate l!! about the hinge 2l from a position parallel to the coil 2 to any inclined position.4 This movement is accomplished by providing a guide aperture or slot at the end Illa of the metal plate for a threaded bolt 24 extending upwardly from the base 2|, and providing an interiorly threaded nut 26 for engaging the bolt 25, which, by its movement, acts on the upper plate la against the reaction of coil spring 25 on bolt 24 below plate l0. By the movement of the plate lil in this manner, a variation in the distributed capacity of the wave conductor is obtained, thereby effecting a variation in the electrical length of the wave conductor. With this arrangement the distributed inductance and capacity per unit length is not of uniform magnitude along the wave conductor. It is understood, however, that other adjusting means may be used by which uniform distributed induct-ance and capacity is obtained for every position of the adjustable plate, for example, by moving plate i@ in such a way as to be always in a position parallel to the wave coil 2.

While I have described my invention as embodied in a specific form and as operating in a specific manner for purpose of illustration, it should be understood that I do not limit my invention thereto, since various modifications will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

I claim:

1. In a radio receiving system for energies containing high frequency signal energy and interfering energy, a radio receiver, an oscillatory circuit constituting the input circuit of said radio receiver, a plurality of antennas of different electrical characteristics connected to a common electrical point in said oscillatory circuit, one of said antennas being a simple wire conductor having one end thereof directly connected to said common point, the other one of said antennas also being a simple wire conductor connected to said common point through the intermediary of a tunable wave conductor having one end of said wave conductor connected to said common point, while one end of said last-mentioned antenna is connected to the tuning means capacitively coupled to said wave conductor, and additional coupling means between said wave conductor and said oscillatory circuit comprising a condenser coupling at said wave conductor and an inductive coupling at said oscillatory circuit.

2. A radio receiving system as set forth in claim 1 wherein said last-mentioned coupling means comprises a metal strip adjustably positionable in proximity to said wave conductor and electrically connected to an inductance coil in proximity to the inductance of said oscillatory circuit.

3. A radio receiving system as set forth in claim 1 wherein said last-mentioned coupling means comprises a metal strip adjustably mounted longitudinally of and transversely from said wave conductor and an inductance coil connected to said metal strip and adj ustably mounted with respect to the inductance of said oscillatory circuit.

4. In a radio receiving system for energies containing high irequency signal energy and interfering energy, a radio receiver, an oscillatory circuit constituting the input circuit of said radio receiver, and a plurality of antennas of different electrical characteristics connecte-d to a common electrical point in said oscillatory circuit, one of said antennas being a simple wire conductor having one end thereof directly connected to said common point, the other one of said antennas also being a simple wire conductor connected to said common point through the intermediary of a wave conductor having one end of said wave conductor connecte-d to said common point, while one end of said last-mentioned antenna is coupled to said wave conductor,.the electrical length of the wave conductor being a substantial fraction of the wave length of the desired signal, such electrical length being other than that which would produce resonance at the frequency of the desired signal.

5. In a radio receiving system for energies containing high frequency signal energy and interfering energy, a radio receiver, an oscillatory circuit constituting the input circuit of said radio receiver, and a plurality of antennas of different electrical characteristics connected to a common electrical point in said oscillatory circuit, one of said antennas being a simple wire conductor havingone end thereof directly connected to said common point, the other one of said antennas also being a simple wire conductor connected to said common point through the intermediary of a tunable Wave conductor having one end of said wave conductor connected to said common point, while one end of said last-mentioned antenna is adjustably coupled to said Wave conductor.

6. In a radio receiving system for energies conelectrical characteristics connected to a common electrical point in said oscillatory circuit, one of said antennas being a simple wire conductor having one end thereof directly connected to said common point, the other one of said antennas also being a simple Wire conductor connected to said common point through the intermediary of a tunable wave conductor having one end of Sadi wave conductor connected to said common point while one end of said last-mentioned antenna is connected to a metallic plate capacitively coupled to said Wave conductor.

7. A receiving system as set forth in claim 6 wherein the last-mentioned antenna is grounded at the end thereof opposite its connection to the metallic plate.

8. A radio receiving system as set forth in claim 4 wherein the second mentioned antenna is coupled to the Wave conductor by a distributed capacity coupling.

9. A radio receiving system as set forth in claim 4 wherein the second mentioned antenna is coupled to the wave conductor by an adjustable distributed capacity coupling.

10. In a radio receiving system for energies containing high frequency signal energy and interfering energy, a radio receiver having an input circuit, a plurality of antennas of different electrical characteristics connected to a common electrical point and means to apply the resultant potential developed at that point to said input circuit, one of said antennas being a simple wire conductor having one end thereof directly connected to said common point, the other one of said antennas also being a simple wire conductor connected to said common point through the intermediary of a Wave conductor having one end of said Wave conductor connected to said common point, While one end of said last mentioned antenna is coupled to said wave conductor, the electrical length of the wave conductor being a substantial fraction of the wave length of the desired signal, such electrical length being other than that which would produce resonance at the frequency of the desired signal.

11. A radio receiving system as set forth in claim 10 wherein the second mentioned antenna is coupled to the Wave conductor by a distributed capacity coupling.

12. A radio receiving system as set forth in claim 10 wherein the second mentioned antenna is coupled to the Wave conductor by an adjustable distributed capacity coupling.

13. A radio receiving system as set forth in claim 1'0 wherein the second mentioned antenna is grounded at one end and coupled to the wave conductor at the other end by an adjustable distributed capacity coupling.

LOUIS COHEN.

REFERENCES CITED The following references are of record in the le of this patent:

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